The present invention relates to a hydraulic pump with a built-in electric motor in which an electric motor and a pump unit that are disposed in tandem along the axis of rotation are received in a common housing.
As disclosed, for example, in JP-A-0988807, a hydraulic pump with a built-in electric motor of the type in which an oil-immersed electric motor and a hydraulic pump unit are disposed in tandem along the axis of rotation and interconnected by a common shaft whereby a drain oil discharged from the hydraulic pump unit within a common housing is introduced into and discharged to the outside of the oil-immersed electric motor to thereby cool the electric motor with the pump drain oil, has been known in the art.
Although the hydraulic pump with a built-in electric motor of the type in which the built-in electric motor is immersed and cooled with the drain oil from the pump unit is excellent in cooling efficiency due to the fact that structurally the electric motor coils which are subject to cooling is in direct contact with the hydraulic oil or the cooling medium, in the case where water is introduced into the hydraulic oil or the hydraulic oil itself is an aqueous hydraulic oil, difficulties are encountered in that not only there is the danger of causing such trouble as an electric short-circuiting inside the electric motor, but also very fine metal foreign particles produced within the rotating electric motor tend to enter the hydraulic oil thus making a filter treatment unavoidable for the recirculation of the drain oil and requiring additional time and labor for the maintenance of the hydraulic system including a frequent changing of filters, etc.
Further, in the conventional hydraulic pump with a built-in electric motor, the electric motor-is of the oil immersed construction and its installation posture is permanently fixed so that not only there is a limitation to the installation place within machinery which utilize such pump, but also a piping connection to the hydraulic oil reservoir tank is required thus making it necessary to suffer a certain degree of complication in the construction of the installation portion.
In view of the foregoing deficiencies in the prior art, it is the primary object of the present invention to provide a hydraulic pump with a built-in electric motor capable of not only simultaneously achieving the cooling of a built-in electric motor and the prevention of contamination of a hydraulic oil due to the rotation of the electric motor, but also preventing the occurrence of electrical troubles with the built-in electric motor even if a water-containing hydraulic oil or aqueous hydraulic oil is fed and discharged. Also, it is another object of the present invention to increase the degree of freedom of design for selecting the installation positions or to make it possible to eliminate the need for piping connection to a reservoir tank.
In accordance with the present invention, there is thus provided a hydraulic pump with a built-in electric motor in which an electric motor and a pump unit are arranged in tandem fashion and accommodated within a common housing. More particularly, the housing is in the form of a metal box having a rectangular parallelepiped external shape and forms an electric motor frame fixedly accommodating a stator of said electric motor therein. A space in the metal box on the electric motor side is separated as a dry or atmospheric space from the internal space of the pump unit by a seal mechanism. At least one hydraulic oil receiving chamber is formed in the peripheral wall of the metal box, and that the hydraulic oil receiving chamber is communicated with a passage for receiving a return oil from the outside and a passage leading to the suction port of the pump unit.
Here, the so-called seal mechanism of the present invention means all kinds of oil leakage seal mechanisms capable of transmission of rotation, e.g., those which smoothly transmit the rotation of the electric motor to the rotor of the pump unit and prevent the leakage of the oil from the internal space of the pump unit to the space on the electric motor side. As regards specific examples of such seal mechanism, where the rotary shaft of the electric motor and the pump unit is composed of a single common shaft, for example, it is possible to cite an annular oil seal disposed adjacent to a bearing in a pump unit case between the electric motor and the pump unit, or alternatively, where the rotary shaft of the electric motor and the rotor rotating shaft of the pump unit are disconnected separate shafts, it is possible to cite a magnetic coupling with an oil leakproof seal so designed that magnets are disposed on the inner peripheral surface of a coupling socket provided on the forward end of the rotary shaft of the electric motor, that corresponding magnets are also disposed on the end of the rotor rotating shaft of the pump unit that is inserted in the socket through a diametrical gap, that the end of the rotor rotating shaft is covered with a seal cap through an annular gap between the magnets and that the opening flange of the seal cap is sealingly fixed to the case side of the pump unit.
In the hydraulic oil pump with a built-in electric motor according to the present invention, the housing forms the electric motor portion and also the electric motor portion within the housing is disposed in the dry space separated from the internal space of the pump unit by the seal mechanism whereby the hydraulic oil sucked into the pump unit flows through the hydraulic oil receiving chamber disposed in the housing peripheral wall separately from the dry space and it does not contact with the rotating parts of the electric motor; thus, there is no danger of the hydraulic oil being contaminated with metal foreign particles emitted from the rotating electric motor and also there is no danger of electrical troubles being caused within the electrical motor due to the hydraulic oil even if the hydraulic oil contains water or the hydraulic oil itself is an aqueous hydraulic operational fluid. Moreover, in the hydraulic pump with a built-in electric motor according to the invention, the housing itself forms a liquid-cooling jacket for cooling the electric motor and therefore the cooling of the electric motor is attained effectively. While, in this case, the generation of heat from the electric motor is caused mainly by the windings of its stator, the stator is attached to the metal box forming the housing and thus the heat generated from the stator windings is directly transmitted to the metal box by heat conduction, thereby ensuring an effective cooling owing to not only the heat dissipation effect of the outer surface of the metal box itself but also the fact that the heat is absorbed through heat conduction by the hydraulic oil in the hydraulic oil receiving chamber through the metal box.
The pump unit is driven by the rotation of the electric motor so that the hydraulic oil sucked from the hydraulic oil receiving chamber is discharged as a pressurized oil and this-pressurized oil is returned as return oil to the hydraulic oil receiving chamber after it has performed a work in an external load actuator connected to the pump. Preferably, the drain oil from the pump unit is also introduced into the hydraulic oil receiving chamber so that although the amount of the drain oil is very small as compared with the return oil, it is sufficient to always cause a flow of the hydraulic oil in the hydraulic oil receiving chamber during the operation of the pump and therefore it is effective not only in cooling the electric motor the flow of the hydraulic oil in the hydraulic oil receiving chamber but also in raising the temperature of the hydraulic oil during the warming-up operation in the cold time such as the winter season.
In order to perform the cooling of the electric motor more effectively, it is effective to add a fan radiator which utilizes the rotation of the electric motor. In this case, the fan radiator is mounted to lie along the end plate of the housing (the metal box) on the electric motor side and the fan radiator is rotated by directly connecting it to the end of the rotary shaft of the electric motor. The return oil and the drain oil flowing into the hydraulic oil receiving chamber are passed through the radiator so that the hydraulic oil within the radiator is air-cooled from the outside of the metal box by an air stream caused by the fan. Note that in this case, it is preferable to add a suitable air stream deflecting structure such as a hood to the fan radiator so that the air stream by the fan flows along the housing surface and it is also preferable to further additionally form heat dissipation fins or grooves in the housing outer surface so as to increase the surface area.
In the hydraulic pump with a built-in electric motor according to the present invention, the housing in the form of the electric motor frame having the electric motor stator internally attached thereto is composed of the metal box of the rectangular parallelepiped external shape so that in the section perpendicular to its axis of rotation, there are four areas of substantially triangular shape at the four corners, respectively, between the external contour of substantially rectangular parallelepiped, preferably square shape and the internal circular space for disposing the electric motor and the pump unit therein and therefore these areas can be utilized for the formation of hydraulic oil receiving chambers.
For instance, assuming that the external dimensions of the square section of the metal box are about 280 mm*280 mm, the inner diameter of the internal space for disposing the electric motor, etc., therein is about 160 mm and the axial length is about 280 mm, the hydraulic oil receiving chambers constituted by the four spaces of substantially triangular sectional shape formed in conformity to the four corner in the peripheral wall of the metal box can be utilized as a reservoir having an inner volume of about 10 liters in total. In the event that a reservoir of a greater volume is required, it is possible to increase the volume by mounting an auxiliary tank to lie on the housing by utilizing the fact that the housing is of the rectangular parallelepiped external shape.
In the hydraulic pump with a built-in electric motor according to the present invention, the housing is rectangular parallelepiped in external shape so that the pump can be installed by selecting either of vertical and horizontal arrangements each selectively using one or the other of the adjoining two sides of the housing as its top surface and the installation posture corresponding to the installation space can be selected. In this case, preferably an opening capable of selectively and detachably mounting therein an air breather and an oil level measuring window is formed in each of the two sides so that as for example, the air breather is mounted in the opening formed in one of the sides serving as the top surface and the oil level measuring window is attached to the opening in the other side in the case of the vertical arrangement, whereas in the case of the horizontal arrangement the mounting of the air breather and the oil level measuring window is reversed with each other. Similarly, when mounting an auxiliary tank, one of these openings is used for communicating the tank with the hydraulic oil receiving chamber and the tank is formed with openings each for selectively mounting the air breather and the oil level measuring window therein in place of the opening used for such communicating purposes.
The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description of its embodiments made with reference to the accompanying drawings.